Narrowband Oxygen Sensor Function

Narrowband oxygen sensors are extremely inprecise. They can't tell the computer the exact air/fuel ratio like wideband oxygen sensors. Technically narrowband oxygen sensors produce an exponential voltage signal, whereas wideband oxygen sensors produce a linear current signal. When the air/fuel ratio is perfectly balanced, a narrowband O2 sensor produces a signal of about 0.5 volts (500 millivolts). When the fuel mixture goes rich, even just a little bit, the O2 sensor's voltage output shoots up quickly to its maximum output of close to 0.9 volts. Conversely, when the fuel mixture goes lean, the sensor's output voltage drops to 0.1 volts.